Microanalysis

Microanalysis is the investigation of tiny, microscopic parts of object using physical and chemical methods. In order to carry out the analysis, miniscule samples – almost invisible to the naked eye – are removed from the paint layer. These can be prepared as cross sections, which allow us to see all of the paint layers, from the ground and lower paint layers all the way up the varnish and dirt on the surface of the painting. The aim of microanalysis is to identify the constituent materials of a painting, including the stratigraphy of the paint layers, as well as providing clues about the methods of the painting’s manufacture. Such clues may allow conservators and conservation scientists to ascertain information about the dating and attribution of a painting, and to compare the use of painting materials with different paintings by known artists (see the video).

The paintings were analysed, first by microscopic inspection of the paint surface, and then by cross-sectional analysis. Cross sections were viewed using a binocular microscope at a range of different magnifications, and some samples were investigated further by electron microscopy. The comparative microscopic examination of cross section samples from the Tallinn, Copenhagen and Glasgow paintings reveals the relative similarity of the colour palette for each painting in their use of 16^th-century pigments such as vermilion/cinnabar, red lake, copper resinate/verdigris, azurite, lead-tin yellow, ochre, lead white, chalk, carbon-based black.

Typically, the underlying panel of a 16^th-century Netherlandish painting is covered with a relatively thick layer of white ground made up of chalk and animal glue. In cross section, a thin layer of imprimatura, which is often lead white in oil, may be seen. The coloured passages were built up in different ways depending on the pigments involved, but typically consist of opaque paint layers with translucent glazes on top. A transparent varnish sits on top of the paint layers and saturates the paint film, making darks appear darker.